Using shutter button to take one photo with manual focus

I have a rather basic problem. Anyone know how to use the shutter button to take just one snap with manual focus? I'm trying to use manual focus with infinity distance, but if I take a shot after leaving ALT mode, and come back to ALT mode to check the focus distance, manual focus is changed to OFF. I already have AF-Point Zoom, Servo AF and Continuous AF set to OFF.

I have a rather basic problem. Anyone know how to use the shutter button to take just one snap with manual focus? I'm trying to use manual focus with infinity distance, but if I take a shot after leaving ALT mode, and come back to ALT mode to check the focus distance, manual focus is changed to OFF.

I seem to recall having occasional trouble with an override set in the Enhanced Photo Operations menu, but I don't remember whether it was subject distance.I could not reproduce it later. If it's there, it might be due to an uninitialized variable?